Plugs and leads is a good first port of call, a bit of damp in the system maybe by what you say..
If that doesn't cure your problem then perhaps dizzy cap/rotor..fuel/ecu relays, water temp sensor, clogged throttle body internal, blocked engine breathers, could even be other sensors/senders like hall and crank but it's all guessing really from here, could even be dodgy fuel..
Anyways see how you go, one thing at a time and at least your eliminating less expensive obvious things as you go..
How's that

hope it helps..